Ok forecasts are forecasts, indications, can't be trusted, blah blah, I get that. But can anyone explain why the following weather forecast (from Elders, I beleive it is a BOM source? most are the same) describes Tue as "Rain" when it has a 90% chance of 5-10mm, but describes Wednesday as "Possible shower" when it has same 90% chance and a greater 10-20mm. WTF?

Possible explanations:

1. Description is daylight hours (e.g. mostly sunny) but chance/amount is 24hr?
2. One describes spread out precipitation the other concentrated.
3. I'm a retard
4. They're all retards

Rain generally equates to widespread, continuous precipitation. Showers have gaps between them. The summaries are usually hopeless by themselves though, the words give a much better idea of what's going on.

On 26/09/2013 gaetanr wrote:>There is a great comment on reddit that explain those percentage : http://www.reddit.com/r>Documentaries/comments/1n1f2d/can_anyone_recommend_a_doco_about_understanding/ccelaoe>

"Chance of rain describes the likelihood of receiving a measurable amount of rain (>0.2mm) during the day at that location. For example, if the chance of rain for Mildura is 30%, it means that on 3 out of 10 days with similar weather conditions rainfall will be measured in the Mildura rain gauge. Where there may be a 30% chance of any rainfall, there is also a 70% chance of not receiving any rainfall at all."

This was quite interesting too from BOM glossary, different to how I initially interpreted it.

Rainfall amount

Rainfall amount indicates the likely amount of rain in millimetres for the forecast period. Sometimes rain falls in a patchy pattern across an area with some locations receiving a heavy shower while an area nearby might miss out completely. On these days the rainfall range may be quite large, e.g. 5 to 30 mm. When steady rainfall is expected over a wide area, the range may be smaller, e.g. 10 to 15mm.

I believe that these figures are generated from their computer modelling and do not have input from from an actual forecaster . the figures come from the agriculture part of the web site . elders use this data